Gaging machine



R. E. ES'CH GAGING MACHINE Filed Dec.

Dec. 2, w69

INVENTOR. ROBERT E. ESCH ATTORNEY United States Patent O 3,481,043GAGING MACHINE Robert E. Esch, Kettering, Ohio, assignor to The BendixCorporation, a corporation of Delaware Filed Dec. 12, 1967, Ser. No.690,015 Int. Cl. B23f 23/08; B23q 17/04; G01b 3/00 U.S. Cl. 33-174 4Claims ABSTRACT OF THE DISCLOSURE A numerically controlled measuringmachine particularly adapted for precise measurement of surface contourof parts. Measurements are continuously made along a'gaging axis as thetransducer means and part are relatively positioned along a second orpositioning axis. Reference or nominal gaging signals in the gaging axisare automatically obtained which are correlated with the relative.locations along the positioning axis. These reference signals arecompared with the measurements obtained to determine the extent ofdeviation in contour.

BACKGROUND OF THE INVENTION This invention relates to machines fordetermining the dimensional configurations of parts.

In machining a part, it is necessary that the cutter or other formingmeans be located in the proper position relative to the part because itis this position which determines the part configuration. Currentmachine tools, particularly those involved in numerical controlmachining, locate the part and cutter with high precision.

Parts produced by such machines must be inspected. Such inspectionequipment must by its very nature be of greater precision than themachine which produced the part undergoing inspection. An accepted ratiospecifies that the tolerance allowable to the gagemaker is one-tenth ofthe tolerance allowed in the manufacture of the part to which hisequipment will be applied.

In prior known gaging machines of the general type here involved, boththe part and the gaging transducer have been positioned with extremeaccuracy to nominal positions with the reading of the transducer thenindicating deviations of the part from nominal. The problem to thegagingmachine manufacturer in machines of that type is one ofpositioning. This will be apparent when it is considered that availabledriving and positioning equipment is utilized to its fullest extent inpart producing machine tools and the gagemakers requirement for accuracyis Well beyond this in his similar equipment provided for inspectionrather than cutting or forming. Even though equipment is available toaccurately measure and signal the position of various components in, forexample, numerically controlled gaging equipment, the need to direct anddrive the transducer and part to the precise relative positionsnecessary to achieve the required accuracy has required extremelyprecise and expensive positioning equipment and has in many instanceslimited the degree of accuracy which could be achieved.

SUMMARY OF THE INVENTION Through the present invention, the necessityfor precise positioning of either the part or transducer is eliminated,making possible greater accuracy in more economical equipment.

In one aspect of the present invention the primary gaging sensor ortransducer which provides a gaging signal is carried for movement in thegaging direction. Its signals are used to automatically position thetransducer itself toward maintaining a desired reference displacementbetween transducer and part. It is not essential through 3,481,043Patented Dec. 2, 1969 ICC the present invention that the transducervpositioning be precise because its position is detected and signalled bya second transducer. The joint signals obtained are accuratelyrepresentative of the disposition of the part surface in the gagingdirection irrespective of the positioning accuracy of the primarytransducer itself.

In another aspect of the present invention, the necessity for precisepositioning is eliminated by signalling the relative positions of partand transducer along a second or positioning axis as gaging signals areobtained along the gaging axis. Data means are included whichautomatically respond to positioning axis signals to provide correlatednominal signals in the gaging direction. These nominal signals arecontinuously compared with the gaging signals to detect deviations inpart configuration from nominal.

BRIEF DESCRIPTION OF THE DRAWING The drawing illustrates, in blockdiagram form, an exemplary embodiment of a machine or systemincorporating features of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT For purpose of illustrating thepresent invention, an exemplary part 1 has been selected Whoseconfiguration or upper contour is defined by correlated displacementsalong mutually perpendicular axes. The first axis in this illustrativeexample is Z or vertical and is the one along which displacements of theupper surface of the part which determine its configuration or contourin this direction will be sensed and signalled. In this application, thepart itself is bodily and continuously displaced along a second axis,identified as X, which is horizontal and at right angles to the Z axis.

The function of this machine is to explore the configuration and contourof the upper surface of part 1 rapidly and accurately and to determineits deviations from the nominal or desired contour and whether thesedeviations are within acceptable limits or tolerances. This isaccomplished by measuring the displacements of the upper part surfacealong the Z axis and signalling these displacements while continuouslytraversing the part along the X axis and signalling the part positionalong this axis. Output signals along the Z axis are continuouslycompared with nominal or reference signals for this axis provided bydata means controlled by the actual positions of the part along the Xaxis. While the direction of the part movement in the illustratedembodiment is straight line, it will be appreciated that the relativemovement of the part and the transducer of the Z axis could well berotary or translatory, or a combination of either. Where relativemovement is defined herein as being along an axis, it is intended todesignate such a relative displacement whether rotary, translatory, orboth.

The part 1 is mounted on a carriage 2 supported for movement to theright and left along the X axis. Carriage 2 is driven for movement inthis direction by motor 3 through screw drive 4. A rotary encoder 5 actsas a transducer to signal in incremental or digital form the positionsof carriage 2 in the X direction.

The primary transducer or signal means in the Z axis is indicated at 8.While such a transducer4 can be of many forms, in this application isutilized an Electrojet cartridge manufactured by The Bendix Corporation.This type transducer includes a differential transformer arrangementwherein a work contacting stylus 10 positions an armature relative tointernal windings. When the armature is centered relative to thesewindings, the signal is nulled. Displacements in either direction fromthis centered position will result in signals of a magnitude varyingwith the magnitude of the displacement and of a phase relationshipdetermined by its direction. Such signals are provided through output11.

Transducer 8 is suported by a carriage 12 driven by motor 14 throughscrew 15. Transducer 8 thus effectively signals deviations indisplacement of the part surface from the reference displacementrelative to carriage 12 necessary to null the output of transducer 8.

In most applications, the changing contour of the upper surface of part1 in the Z direction will exceed the effective gaging range oftransducer 8 were the transducer body fixed. The transducer then must bedisplaced along this axis through the motor 14 and carriage 12, asearlier described, while the carriage position itself is signalled by atransducer encoder 18 providing digital output signals through 20.

Thus it is seen that transducer 8 and encoder 18 jointly signal thedisposition of the surface of part 1 along the first or Z axis.

For command signals and data input to the machine or system, a numericalcontrol console 21 is employed. This can be a Bendix Dynapath controlmanufactured by The Bendix Corporation. This' console includes the tapeinput 22. circuitry providing input logic and interpolator functions 23,an error register 24, and a digital to analog converter 25 provided forpurposes as will be later explained. The tape input 22 provides thevarious major command signals, such as the commencement and terminationof functions. It also supplies dimensional data in the form ofcorrelated nominal relationships between X and Z displacements in theform of conventional information blocks. The interpolator of the consoleinterpolates between the points defined and provided by the input tapeinformation and adds additional correlated data in X and Z, along thefirst and second axes, for points between those provided by the tapeinput.

In operation, tape input 22 through input logic and interpolator unit 23provides an output or command signal to motor 3 commencing continuoustraverse of carriage 2 and part 1 in a given direction along the secondor X axis and relative to transducer 8. The circuit to motor 3 is anopen loop rate control.

As the carriage 2 traverses, encoder 5 provides a digital output signalto the console 21 which is responsive to the relative dispositions oftransducer 8 and part 1 along the X axis.

The signal from encoder is automatically correlated within console 21with the input signals from tape input 22, or from the interpolator forpoints therebetween, and a signal of the nominal or referencedisplacement of the part surface along the Z axis for that particularrelative position along X of transducer 8 and part 1 is provided toerror register 24. Such correlated output signals are provided to errorregister 24 continuously and in digital form `as output signals areprovided by encoder 5.

The system operating along Z axis is basically of a slave typefunctioning to drive and position transducer 8 to its null point.Transducer 8 and drive motor 14 for its carriage 12 are effectively in aclosed loop. Whenever a signal other than null is provided fromtransducer 8, it is amplified at 3d. It is further amplified in servoamplifier 31 and is provided as an energizing signal to motor 14,automatically driving motor 14 and positioning carriage 12 to move thebody of transducer 8 relative to its part engaging stylus to seek thenull position although the circuit is not necessarily continuouslynulled.

Thus, as carriage 2, and part 1, which it supports, are traversed alongthe X axis, transducer 8 is continuously positioned to follow the upercontour as a slave positioning not directly under the control of thenumerical control unit 21.

As earlier mentioned, the displacement of the upper surface of part 1 inZ direction is thus effectively signalled lby the interrelated signalsfrom transducer 8 and from encoder 18 irrespective of the actualpositions of carriage 12.

Signals from encoder 18, which are in digital form, are provideddirectly to error register 24. Error register 24, as earlier described,is also provided with nominal or reference Z axis signals in digitalform correlated to the relative positions of the part and transducer inthe X axis. In error register 24 the reference signal and output signalfrom encoder 18 are compared. Any difference is converted from digitalform to analog in converter 25 for later comparison with the analogsignals from transducer 8. The signals from transducer 8, amplified at30, are brought to summing amplifier 35, which is also connected toconverter 25. Thus, these signals are compared and the difference, whichrepresents the deviations in displacement of the part surface 1 alongthe Z direction from nominal, is supplied to an output as desired. Inillustrated example, these deviations are provided to a recorder 36. Thepresent invention is adaptable to input gaging signals of analog ordigital form, or combinations of both, and will provide output signalsin analog or digital form, by the use of suitable circuit converters asdesired.

Thus, it is seen that a machine or system has been provided forprecisely determining the dimensional configuration of the surface of apart rapidly and accurately. the necessity for precise positioning ofeither transducer or part is eliminated while providing gaging resultsof the highest accuracy.

While the form of apparatus herein described constitutes a preferredembodiment of the invention, it is to be understood that the inventionis not limited to this precise form of apparatus, and that changes maybe made therein without departing from the scope of the invention.

What is claimed is: 1. A machine for determining the dimensionalconfiguration of the surface of a part defined nominally by correlateddisplacements along first and second axes, said machine comprising:

first signal means responsive to the disposition of the surface of apart along said first axis for generating a signal representative ofsaid disposition,

second signal means responsive to the relative disposition of said firstsignal means and said part along said second axis for generating asignal representative of said relative disposition,

data means responsive to the signal generated by said second signalmeans providing reference first axis signals correlated with therelative dispositions of said first signal means and said part alongsaid second axis, and

comparison means responsive to deviations between the signal generatedby said first signal means and the reference signals of data means forsignalling deviation of said surface from a surface corresponding tosaid reference signals.

2. A machine for determining the dimensional configuration of thesurface of a part defined nominally by correlated displacements alongfirst and second axes, said machine comprising:

first signal means responsive to the disposition of the surface of apart along said first axis for generating a signal representative ofsaid disposition,

first drive means for relatively positioning the part and said firstsignal means along said first axis,

second signal means responsive to the position of said rst signal meansalong said first axis for generating a signal representative of saiddisposition,

second drive means for relatively positioning said part and said firstsignal means along a se'cond axis,

third signal means responsive to the relative disposition of said firstsignal means and said part along second axis for generating a signalrepresentative of said relative disposition,

data means responsive to the signal generated by said third signal meansproviding reference first axis signals correlated with the relativedisposition of said rst signal means and part along said second axis,and

comparison means responsive to both said first and said second signalmeans and thus to the displacement of the part surface along said rstaxis for comparing such displacement with the reference rst axis signalsas correlated with the relative positions of the first signal means andpart along the second axis.

3. A machine for determining the dimensional configuration of a part,said machine comprising:

a base,`

means for supporting a part to be measured on said base,

a carrier mounted for movement on said base along a gaging axisintersecting the surface of said part,

first signal means on said carrier responsive to deviations indisplacement of the part surface along said gaging axis from a referencerelative displacement withrespect to said carrier for generating asignal representative of said deviation,

drive means for positioning said carrier along the gaging axis, controlmeans responsive to the signal generated by said first signal meansoperatively connected to said means for control thereof and movement ofsaid carrier in a direction to reduce deviations from the referencedisplacement between part and carrier,

second signal means responsive to the position of said carrier along thegaging axis and with respect to said base and the part supported thereonfor generating a signal representative of said position, and

means combining the signals from said first and second signal means forsignalling the displacement of said part surface along the gaging axisirrespective of the accuracy of positioning of said carrier.

4. A machine for determining the dimensional configuration of thesurface of a part defined nominally by correlated displacement along apositioning axis and a gagin axis, said machine comprising:

a base,

a movable support on said base for carrying a part to be measured alongsaid positioning axis,

a carrier mounted for movement on said base along said gaging axisintersecting the surface of said part,

first signal me'ans on said carrier responsive to deviations indisplacement of the part surface along said gaging axis from a referencerelative displacement with respect to said carrier for generating asignal representative of said deviations,

drive means for positioning said carrier along the gaging axis,

control means responsive to the signal generated by said first signalmeans operatively connected to said drive means for control thereof andmovement of said carrier in a direction to reduce deviations from thereference displacement between part and carrier,

second signal means responsive to the position of said carrier along thegaging axis and with respect to said base and the part supported thereonfor generating a signal representative of said position,

third signal means responsive to the relative disposition of said firstsignal means and said support and part along said positioning axis forgenerating a signal representative of said relative disposition,

data means responsive to the signal generated by said third signal meansproviding reference gaging axis signals correlated with the relativedisposition of said first signal means and part along said positioningaxis, and

means responsive to signals generated by said first and second signalmeans and said reference gaging axis signals as correlated with therelative positions of the first signal means and part along thepositioning axis for providing output signals representative of thedeviation of said part surface from a surface corresponding to saidreference signals.

References Cited UNITED STATES PATENTS 2,835,042 5/1958 Tandler et al.33-174 2,901,105 8/1959 Harder 33-174 3,135,055 6/1964 Butler et al.33-174 3,250,012 5/1966 Hilton et al. 33-174 SAMUEL S. MATTHEWS, PrimaryExaminer UNITED STATES PATENT OFFICE CERTIFICATE' OF CORRECTION PatentNon 3,481,043 Dated December 2, 1969 Inventor(s) RObert E. ESCh.

It is certified that error `.appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

IN THE SPECIFICAToN Column 3, line 3, .suported. should read supported.

Column 4, line 25, .the. should read The--.

IN THE CLAIMS Claim 3: Column 5, line 26 --drveshould be inserted before.means.

slanaumn Smm 00T 6 -m Attest:

mwa Mnewhmrr'. WILLIAM E. suHuYnER, JB. Attesting Officer Connnsslonerof Patents

